This invention relates to an electromagnet for use in an electromagnetic clutch known in the art.
A conventional electromagnet for use in the electromagnetic clutch comprises an annular core with an annular groove, an annular coil member placed in the annular groove, and a thermal fuse attached to the annular coil member.
The annular groove has an opening surface and a closed bottom surface which are opposite to each other in an axial direction of the annular core. The annular coil member has a first surface facing the closed bottom surface and has a second surface opposite to the first surface in an axial direction of the annular coil member. The thermal fuse is placed on the second surface of the annular coil member.
The annular core further has a through hole at a particular portion of the closed bottom surface. The annular coil member further has two lead wires which are extracted outwards from the annular groove through the through hole.
In the conventional electromagnet, the annular coil member has a center line coaxial with that of the annular core. As a result, an overall area of the first surface of the annular coil member is kept in contact with the closed bottom surface of the annular groove.
With this structure, the lead wires are led into the through hole through an area which is between the first surface of the annular coil member and the closed bottom surface of the annular groove. Thus, the lead wires can possibly be brought into tight contact with the annular core to thereby damage or break the electrical insulation of the annular coil member.
In order to remove the possibility of occurrence of damage, a spacer having a sufficient size is arranged between the annular coil member and the annular core throughout the overall area of the closed bottom surface of the annular groove. In this case, however, the thermal fuse may possibly protrude from the annular groove to be brought into contact with a pulley of the electromagnetic clutch in the manner known in the art.